By Lee Min-youngSinger-songwriter Maeng Yuna has died from a heart attack at the age of 29.According to her agency JH Entertainment Tuesday, Maeng was found dead at her home on Dec. 26. Doctors later concluded that the cause of her death was an acute heart attack.She did not have any serious pre-existing medical conditions, although she was under stress as she was preparing to release her new album in June, the agency said.Maeng made her debut in Japan in 2007 with the soundtrack for the TV show "Spring Waltz" and continued her music career in Korea. In total, she released 10 albums ― two full-length albums and eight singles.She was a daughter of Maeng Jung-ho, former manager of singer Cho Yong-pil.